Nice cool day, good cloud cover with no rain, light breeze just made for putting a few over the screens. Took out the Glock 17L and ran the same loads that I ran through the Glock 17 last time (on 08/08/2008) for the sake of comparison.

The test data yielded some surprises as to how increasing the barrel length from 4.49" to 6.02" would effect the velocity of this ammunition. Most surprising were the minimal gains of 20-40 fps. regardless of bullet weight despite the 1.53" longer barrel. All ammunition was from the same exact box and lot and the ambient temperature and humidity were much the same as when these loads were run through the Glock 17. Eh, go figure.

I was really rather surprised at the outcome of this chronography session.

Just "goofing around" became "an experiment" which then became a "challenge" to those assumptions that I had always held as "fact" which then evolved into me "questioning" that which I have always chosen to carry based upon that which I have recently discovered.

While I had expected that the 147 gr. subsonics would see very little velocity increase, I was laboring under the assumption of obtaining much improved velocity from the lighter (supersonic) loads in the Glock 17L with its 6.02" barrel, especially the 115 gr. stuff.

Reflecting upon the origins of this assumption, I believe that it was imparted to me from two sources, the first being a gunsmith of my personal acquaintance during my mis-spent youth and the second being my Dad, of all people. Both sources always offered the suggestion that one could realistically expect a 40-50 fps increase in muzzle velocity from the commonly available handgun calibers (.38 Special, 9mm, .357 Magnum, .40 S&W, .45 ACP, what have you) per additonal inch of barrel length and it seemed like solid common sense to me.

So, quite frankly, I had anticipated seeing somewhere between 100-150 fps depending on how "hot" the particular round was loaded and was expecting to see such an increase from the Fiocchi 115 gr.FMJ (9AP) because it offered quite a bit of muzzle blast and flash as well as a markedly stronger recoil impulse than any load tested, all indicators of a "hot" load to be sure. That it only increased by 52.8 fps with the extra 1.5" of tube surprised the heck outta me and you can be quite sure that I am all done assuming such things.

Based upon the marginal increases (20-40 fps, give or take a bit) displayed across the range of bullet weights/velocities, I can only conclude that the powders loaded within these rounds and the quantities thereof, are balanced for an "optimal runway length" of 4" to 5" (or 100mm-125mm) and that any increase in barrel length over that range will yield nominal increases at best as the expansion volume diminishes (linearly). Past that point, internal bore friction must begin to equal and then eventually exceed any gainful effects produced by the rapidly decreasing expansion volume as barrel length increases.

In short, based upon these results, I have now begun to reconsider my year-'round employment and outright preference for the full sized "service" weapons (in my case, the Glock 17) in favor of the mid-size pistols (again, in my case, the Glock 19) as being the most "size efficient" while still producing "optimal" muzzle velocities and energies without the weight and concealment burdens that accompany the larger "service" platforms while offering nothing in return for assuming those not inconsequential burdens.

Gonna have to run some more tests to confirm these assumptions of course, but it seems that there is a "change" in the not-too-distant future for me and it looks quite a bit like a Glock 19.

As you might have noticed, I tend to run chronograph sessions in August. It seems as if the weather always cooperates, with "ideal conditions" at some point during the month in addition to favoring me with a light breeze.

Decided to drag my poor brother-in-law into the cold and introduce him to the "benefits" of "winter shootin'" (the always vacant outdoor range) since my corrupt influence is the cause of his acquiring the Glock 19 that we used to collect the following data. His chosen SD load (the Remington 147 gr. "Golden Sabre") and mine (the Hornady 147 gr. XTP) seemed to be largely unaffected by the cold and the shorter Glock 19 barrel although our fingers got numb pretty quickly. Beer and wings for lunch took care of that.

Thanks for report CharlieX. I've been procrastinating on getting back out to the range for some chrono time and trigger time. Been cutting up firewood for next winter, getting garden started, and landscaping.